Embodiments of the invention relate to rail vehicles and other off-highway vehicles. Other embodiments relate to electrical energy systems in such vehicles.
Many off-highway vehicles, especially railroad locomotives and other rail vehicles, utilize a diesel engine as a prime mover. In some instances, the diesel engine runs a generator or alternator, which produces electricity used for powering one or more traction motors in the off-highway vehicle. For example, a traction motor may be connected to a vehicle axle via a gear set for moving a wheel connected to the axle.
In a dynamic braking mode of operation, a traction motor is switched from a motoring motor (e.g., being supplied with electricity to rotate an output shaft of the motor) to a generator mode, e.g., rotation of the motor's output shaft (through momentum of the vehicle) results in the generation of electricity at the motor's electrical terminals. The electromagnetic resistance presented by the motor in the dynamic braking mode causes the off-highway vehicle to slow down, without the need to utilize the vehicle's pneumatic-mechanical braking system.
In certain vehicles, electricity generated during dynamic braking operations is stored in an energy storage system located on the vehicle. In many other vehicles, especially certain rail vehicles and other off-highway vehicles that are not equipped with high-capacity energy storage systems, electricity generated during dynamic braking operations is routed to a dynamic braking resistive grid, where it is turned into waste heat that is transferred to a passing airflow for dissipation into the atmosphere.
Dissipating dynamic braking electricity in a resistive grid as waste heat results in reduced levels of vehicle system performance, in terms of overall efficiency and energy use, since the energy captured during dynamic braking is wasted.